package com.softpo.encrption;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Base64;
import android.view.View;
import android.widget.TextView;

import java.security.InvalidKeyException;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.NoSuchAlgorithmException;
import java.security.PrivateKey;
import java.security.PublicKey;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;

//非对称加密
//加密和解密两套密码
//为什么加密和解密不同密码
//费马大定律：勾股定理3平方+4平方=5平方

public class RSAActivity extends AppCompatActivity {

    private PrivateKey mPrivateKey;
    private PublicKey mKeyPairPublic;

    private TextView showKeys;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_rsa);

        initView();

    }

    private void initView() {
        showKeys = (TextView) findViewById(R.id.showKeys);
    }

    //生成公钥私钥
    public void generate(View view) {
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //1、获取公钥私钥生成的对象
                    KeyPairGenerator generator =
                            KeyPairGenerator.getInstance("RSA");
                    //2、初始化,指定密码的长度bit
                    generator.initialize(1024*3);

                    //3、获取公钥和私钥
                    KeyPair keyPair = generator.generateKeyPair();
                    //3.1获取私钥
                    //私钥保存好了，私钥丢了，找不回来了
                    mPrivateKey = keyPair.getPrivate();

                    //3.2获取公钥
                    //公钥丢了，可以通过私钥推到
                    mKeyPairPublic = keyPair.getPublic();

                    //私钥的具体数据，私钥字节数据，保存该数据，文件中，sp
                    //！！！必须进行Base64转换
                    byte[] mPrivateKeyEncoded = mPrivateKey.getEncoded();

                    byte[] mKeyPairPublicEncoded = mKeyPairPublic.getEncoded();

                    //对公钥和私钥中字节数组进行Base64编码
                    final byte[] privateKeyBase64Encode =
                            Base64.encode(mPrivateKeyEncoded, Base64.DEFAULT);

                    final byte[] publicKeyBase64Encode =
                            Base64.encode(mKeyPairPublicEncoded, Base64.DEFAULT);

                    //显示到文本框中
                    showKeys.post(new Runnable() {
                        @Override
                        public void run() {
                            showKeys.setText(
                                    "私钥是： "+"\n"
                                            +new String(privateKeyBase64Encode)
                            +"\n"+"公钥是： "+"\n"+new String(publicKeyBase64Encode)
                            );
                        }
                    });

                } catch (NoSuchAlgorithmException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }

    //使用公钥私钥进行加密界面
    public void encrypt(View view) {
        //使用私钥去加密，使用公钥进行解密
        //举例：
        //阿里巴巴-----传给千锋（其他公司，达内，等等），传文件
        //文件加密，私钥加密文件，传给千锋
        //千锋持有公钥，公钥进行解密
        String check = "100000000,123456";
        switch (view.getId()){
            case R.id.rsaEncrypt:
                try {
                    //1、获取加密引擎
                    Cipher cipher = Cipher.getInstance("RSA");

                    //2、初始化
                    if (mPrivateKey != null) {
                        cipher.init(Cipher.ENCRYPT_MODE,mPrivateKey);
                    }

                    //3、加密
                    byte[] doFinal = cipher.doFinal(check.getBytes());

                    byte[] base64Encode = Base64.encode(doFinal, Base64.DEFAULT);

                    showKeys.setText("RSA加密的数据是： "+new String(base64Encode));

                } catch (NoSuchAlgorithmException e) {
                    e.printStackTrace();
                } catch (NoSuchPaddingException e) {
                    e.printStackTrace();
                } catch (InvalidKeyException e) {
                    e.printStackTrace();
                } catch (BadPaddingException e) {
                    e.printStackTrace();
                } catch (IllegalBlockSizeException e) {
                    e.printStackTrace();
                }
                break;
        }
    }
}
